University of Hertfordshire

From the same journal

From the same journal

Megahertz peaked-spectrum sources in the Boötes field I - a route towards finding high-redshift AGN?

Research output: Contribution to journalArticlepeer-review


  • Rocco Coppejans
  • David Cseh
  • Wendy L. Williams
  • Sjoert van Velzen
  • Heino Falcke
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Original languageEnglish
Pages (from-to)1477-1485
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Early online date25 Apr 2015
Publication statusPublished - 21 Jun 2015


We present a 324.5MHz image of the NOAO Bo\"otes field that was made using Very Large Array (VLA) P-band observations. The image has a resolution of 5.6x5.1arcsec, a radius of $2.05^\circ$ and a central noise of ~0.2mJy\beam. Both the resolution and noise of the image are an order of magnitude better than what was previously available at this frequency and will serve as a valuable addition to the already extensive multiwavelength data that are available for this field. The final source catalogue contains 1370 sources and has a median 325 to 1400MHz spectral index of -0.72. Using a radio colour-colour diagram of the unresolved sources in our catalogue, we identify 33 megahertz peaked-spectrum (MPS) sources. Based on the turnover frequency linear size relation for the gigahertz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources, we expect that the MPS sources that are compact on scales of tens of milliarcseconds should be young radio loud active galactic nuclei at high (z>2) redshifts. Of the 33 MPS sources, we were able to determine redshifts for 24, with an average redshift of 1.3. Given that five of the sources are at z>2, that the four faint sources for which we could not find redshifts are likely at even higher redshifts and that we could only select sources that are compact on a scale of ~5arcsec, there is encouraging evidence that the MPS method can be used to search for high-redshift sources.


This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

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